Study On Electrodeposition Of Ni-cBN Composite Coatings And Properties

In this study, the Ni-c BN composite coatings were prepared by electrodeposition method on the surface of TC4 titanium alloy. The effects of c BN particles content on bath, current density, bath temperature, p H value and the concentration of main salt on the microstructure, microhardness and deposition rate of the composite coatings were studied. Under the condition of this study, the optimum technological parameters were: current density was 1A/dm2, temperature was 60℃, p H=4, the main salt concentration was 350g/L, c BN particles suspended in the plating solution was 10g/L, and the surface active agent was odium dodecyl sulfate.The friction coefficient of Ni-c BN composite coatings decrease with the increase of c BN content in Ni-c BN composite coatings. When th e content of c BN particles in Ni-c BN composite coating is 45.66%, the friction coefficient is 0.408, the wear rate is 0.053 mg.m-1, and the wear resistance is increased by nearly 10 times. The friction coefficient of Ni-c BN composite coatings increase with the increase of the applied load. With the increase of the load, composite coating adhesive wear degree increases, when the load exceeds 8N, the surface of the composite coating begins to crack, while the load reached 10 N, the formation of a crack perpendicular to the direction of wear surface of the composite coatings. The friction coefficient of Ni-c BN composite coating increases with the increase of sliding velocity, but the wear rate decreases with the increase of sliding speed. The wear products were found to have the GCr15 element and a small number of Fe in the wear scar surface, which indicated that the material migration occurred in the sliding friction process. In addition, the O element is also shown in the energy spectrum, which indicates that th ere is a large amount of heat generated during the wear process, so that the coating surface is oxidized to form an oxide film.The oxidation resistance of Ni-c BN composite coatings increased with the increase of c BN content in the coating. In the initial stage of oxidation at high temperature, the oxygen content of Ni-c BN composite coating increased, and the oxidation rate was rapid. With the extension of time, the content of oxygen element in the Ni-c BN composite coating is not obvious, the curve tends to be flat, and the oxidation rate is not obvious. With the increase of oxidation temperature, the increment of oxygen element in Ni-c BN composite coating increased linearly. The oxidation products of Ni-c BN composite coating were analyzed, and the oxidation products were Ni O, and the c BN particles were not changed.The corrosion resistance of Ni-c BN composite coating was studied by using Tafel curve. The corrosion current density of Ni-c BN composite coating decreased gradually with the increase of c BN conten t in Ni-c BN composite coating, and the corrosion rate decreased gradually, and the corrosion resistance was improved. By the electrochemical impedance spectroscopy analysis, with the increase of the content of c BN particles in the Ni-c BN composite coating, the polarization resistance of the Ni-c BN composite coating increased gradually, and the corrosion resistance was improved. The results of these two methods show that the Ni-c BN composite coating has good corrosion resistance.